<s>
In	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
hierarchy	O
,	O
a	O
second-level	B-Protocol
domain	I-Protocol
(	O
SLD	O
or	O
2LD	B-Protocol
)	O
is	O
a	O
domain	O
that	O
is	O
directly	O
below	O
a	O
top-level	O
domain	O
(	O
TLD	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
,	O
is	O
the	O
second-level	B-Protocol
domain	I-Protocol
of	O
the	O
TLD	O
.	O
</s>
<s>
Second-level	B-Protocol
domains	I-Protocol
commonly	O
refer	O
to	O
the	O
organization	O
that	O
registered	O
the	O
domain	O
name	O
with	O
a	O
domain	B-Application
name	I-Application
registrar	I-Application
.	O
</s>
<s>
Some	O
domain	B-Protocol
name	I-Protocol
registries	I-Protocol
introduce	O
a	O
second-level	O
hierarchy	O
to	O
a	O
TLD	O
that	O
indicates	O
the	O
type	O
of	O
entity	O
intended	O
to	O
register	O
an	O
SLD	O
under	O
it	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
.uk	B-Application
namespace	O
a	O
college	O
or	O
other	O
academic	O
institution	O
would	O
register	O
under	O
the	O
ccSLD	B-Protocol
,	O
while	O
companies	O
would	O
register	O
under	O
.	O
</s>
<s>
Strictly	O
speaking	O
,	O
domains	O
like	O
.ac.uk	O
and	O
.co.uk	O
are	O
second	B-Protocol
level	I-Protocol
domain	I-Protocol
themselves	O
,	O
since	O
they	O
are	O
right	O
below	O
a	O
TLD	O
.	O
</s>
<s>
In	O
Austria	O
there	O
are	O
two	O
second-level	B-Protocol
domains	I-Protocol
available	O
for	O
the	O
public	O
:	O
</s>
<s>
In	O
Turkey	O
,	O
domain	O
registrations	O
,	O
including	O
the	O
registration	O
of	O
second-level	B-Protocol
domains	I-Protocol
is	O
administrated	O
by	O
.	O
</s>
<s>
There	O
17	O
active	O
second-level	B-Protocol
domains	I-Protocol
under	O
the	O
.tr	B-Language
TLD	O
.	O
</s>
<s>
Second-level	B-Protocol
domains	I-Protocol
include	O
.com.tr	O
for	O
commercial	O
ventures	O
,	O
.edu.tr	O
for	O
academic	O
institutions	O
and	O
.name.tr	O
for	O
personal	O
use	O
.	O
</s>
<s>
Ukraine	O
second-level	B-Protocol
domains	I-Protocol
include	O
:	O
</s>
<s>
A	O
two-letter	O
second-level	B-Protocol
domain	I-Protocol
is	O
formally	O
reserved	O
for	O
each	O
U.S.	O
state	O
,	O
federal	O
territory	O
,	O
and	O
the	O
District	O
of	O
Columbia	O
.	O
</s>
<s>
There	O
are	O
several	O
second-level	B-Protocol
domains	I-Protocol
which	O
are	O
no	O
longer	O
available	O
.	O
</s>
<s>
Second-level	B-Protocol
domains	I-Protocol
under	O
.au	O
which	O
are	O
no	O
longer	O
available	O
include	O
:	O
originally	O
intended	O
for	O
conferences	O
;	O
for	O
the	O
Australian	O
Academic	O
and	O
Research	O
networks	O
;	O
for	O
general	O
information	O
,	O
and	O
for	O
the	O
X.400	O
mail	O
systems	O
.	O
</s>
<s>
Prior	O
to	O
12	O
Oct	O
2010	O
there	O
were	O
second	B-Protocol
level	I-Protocol
domain	I-Protocol
based	O
on	O
province	O
:	O
</s>
<s>
Since	O
2010	O
,	O
some	O
have	O
been	O
replaced	O
(	O
for	O
example	O
,	O
alberta.ca	O
)	O
while	O
others	O
have	O
remained	O
under	O
the	O
provincial	O
two	O
letter	O
SLD	O
(	O
e.g.	O
,	O
Calgary	O
Board	O
of	O
Education	O
www.cbe.ab.ca	O
)	O
and	O
others	O
were	O
moved	O
to	O
more	O
traditional	O
subdomains	B-Protocol
(	O
www.transportation.alberta.ca	O
)	O
.	O
</s>
<s>
Historic	O
second-level	B-Protocol
domains	I-Protocol
for	O
France	O
included	O
:	O
</s>
<s>
Historic	O
second-level	B-Protocol
domains	I-Protocol
for	O
the	O
Netherlands	O
included	O
:	O
</s>
<s>
In	O
2006	O
the	O
ccTLD	B-Application
was	O
replaced	O
by	O
(	O
for	O
Serbia	O
)	O
and	O
(	O
for	O
Montenegro	O
)	O
.	O
</s>
<s>
Second-level	B-Protocol
domains	I-Protocol
under	O
included	O
:	O
</s>
<s>
Only	O
legal	O
entities	O
were	O
allowed	O
to	O
register	O
names	O
under	O
and	O
its	O
second-level	B-Protocol
domains	I-Protocol
.	O
</s>
<s>
Historic	O
second-level	B-Protocol
domains	I-Protocol
for	O
Tuvalu	O
included	O
:	O
</s>
<s>
Experts	O
say	O
that	O
further	O
restrictions	O
are	O
needed	O
for	O
second-level	B-Protocol
domains	I-Protocol
under	O
the	O
new	O
gTLD	O
,	O
as	O
well	O
.	O
</s>
<s>
For	O
example	O
,	O
second-level	B-Protocol
domains	I-Protocol
under	O
or	O
can	O
be	O
easily	O
misused	O
by	O
companies	O
and	O
therefore	O
are	O
a	O
potential	O
threat	O
to	O
Internet	O
users	O
.	O
</s>
